1. Field of the Invention
The invention relates to a process for rejuvenating solid catalyst particles in a hydrocarbon slurry. More particularly, the invention relates to a slurry hydrocarbon synthesis process in which the slurry is periodically purged of CO, followed by passing catalyst rejuvenating gas through the slurry to restore catalyst activity. Both the purge and rejuvenating gasses may be recycled after removing catalyst deactivating species.
2. Background of the Invention
Slurry hydrocarbon synthesis (HCS) processes are known. In a slurry HCS process a synthesis gas (syngas) comprising a mixture of H.sub.2 and CO is bubbled up as a third phase through a slurry in a reactor in which the slurry liquid comprises hydrocarbon products of the synthesis reaction and the dispersed, suspended solids comprise a suitable Fischer-Tropsch type hydrocarbon synthesis catalyst. Reactors which contain such a three phase slurry are sometimes referred to as "bubble columns", as is disclosed in U.S. Pat. No. 5,348,982. Irrespective of whether the slurry reactor is operated as a dispersed or slumped bed, the mixing conditions in the slurry will typically be somewhere between the two theoretical limiting conditions of plug flow and back mixed. Syngas made from hydrocarbon feedstocks which contain nitrogen (i.e., natural gas) or nitrogen containing compounds (i.e., resids, coal, shale, coke, tar sands, etc.) invariably contains HCN and NH.sub.3 which contaminate the reactive slurry and rapidly, but reversibly, deactivate the catalyst. Certain oxygenates and carbonaceous compounds which are formed in the slurry as by-products of the HCS reaction are also believed to cause rapid deactivation. Deactivation of such catalysts by these species is reversible and catalytic activity is restored (the catalyst rejuvenated) by contacting the deactivated catalyst with hydrogen. The activity of the HCS catalyst in the reactive slurry may be intermittently or continuously rejuvenated by contacting the slurry with hydrogen or a hydrogen containing gas to form a catalyst rejuvenated slurry as is disclosed, for example, in U.S. Pat. Nos. 5,260,239; 5,268,344, and 5,283,216. UK patent publication GB 2,299,767A relates to a batch mode of catalyst rejuvenation in a fully backmixed, continuous stirred tank reactor. However, this process is disclosed as requiring a regeneration time of from 12 to 24 hours every 3-5 days.